Hi Laura
Although it may seem that you are paying a high rate at the moment, there are a few issues that will probably lead to it not bein worthwhile to move your mortgage.
Firstly, Northern Rock will probably charge you an early repayment charge if you pay off your mortgage with them before the deal expires. So we would need to be able to recoup these losses at a minimum to make the switch worthwhile.
Secondly, you purchased with a 100% LTV mortgage plus a loan, so I am guessing that although you have refurbished and possily increased the value of the property, the fact the prices have in general gone down would lead me to think that you would still be at a very high loan to value, making it difficult to find a lender who would lend to you at a cometitive enough rate.
That said, if you feel your property is of a greater value that your mortgage it may be worth looking into, and I would suggest you contact an independent
mortgage broker such as myself who would be able to find the best deal on the market available to you and then see if it is worthwhile moving you when looking at all the costs involved.
I hope that's helpful.
Dan